1. Field of the Invention
The present invention relates to a p-type nitride type 3-5 group compound semiconductor, a process for producing the same, and a compound semiconductor element using the same.
2. Description of the Related Art
A 3-5 group compound semiconductor represented by general formula InxGayAlzN (x+y+z=1, 0<=x<=1, 0<=y<=1, 0<=z<=1) called a nitride type 3-5 group compound semiconductor is well-known as a material for light-emitting devices, such as a ultraviolet, blue or green light-emitting diode or a ultraviolet, blue or green laser diode. The x, y and z in the formula show the composition ratios to nitrogen (N), respectively. In this text, x may be referred to as InN mixed crystal ratio, y may be referred to as GaN mixed crystal ratio, and z may be referred to as AlN mixed crystal ratio.
Among nitride type 3-5 group compound semiconductors, especially those containing InN mixed crystal ratio of 10% or more are important especially for display applications, since the emission wavelength in a visible range can be controlled according to InN mixed crystal ratio. As a manufacture method of the nitride type 3-5 group compound semiconductor, a molecular beam epitaxy method (hereinafter, may be referred to as MBE), a metalorganic vapor phase epitaxy method (hereinafter, may be referred to as MOVPE), a hydride vapor phase epitaxy method (hereinafter, may be referred to as HVPE), etc. are known. Among these methods, the MOVPE method is widely adopted, since a uniform crystal growth covering large area can be attained.
As a method for producing a p-type nitride type 3-5 group compound semiconductor, proposed is a method wherein a nitride type 3-5 group compound semiconductor doped with p-type dopant is grown in vapor phase by MOVPE method, and then heat-treatment is conducted at a temperature of 700–1000° C. under inert gas atmosphere such as nitrogen (for example, JP-A-5-183189).
However, a p-type nitride type 3-5 group compound semiconductor obtained by this method has problems in the electrical properties such that the contact resistance with an electrode metal is high, the ohmic property is inadequate, etc., and the improvement of these problems has been desired.
The object of the present invention is to provide a p-type nitride type 3-5 group compound semiconductor which does not have the above problems in the conventional technology, a process of producing the same, and a compound semiconductor element using the same.